Fixed window creation to use size variables rather than hard coded sizes

Samples/basic/directx10/src/main.cpp

@@ -53,7 +53,7 @@ int APIENTRY WinMain(HINSTANCE ROCKET_UNUSED_PARAMETER(instance_handle), HINSTAN
 	Rocket::Core::Initialise();
 
 	// Create the main Rocket context and set it on the shell's input layer.
-	context = Rocket::Core::CreateContext("main", Rocket::Core::Vector2i(1024, 768));
+	context = Rocket::Core::CreateContext("main", Rocket::Core::Vector2i(window_width, window_height));
 	if (context == NULL)
 	{
 		Rocket::Core::Shutdown();